Asus P5B - Manual (Page 66)

2-38 Chapter 2: Hardware information
2.7.3 Installing the optional fan
Install the optional fan only if you are using a passive cooler or a water cooler.
Installing the optional fan with an active CPU cooler will interfere with the airflow
and destabilize the system.
1. Position the fan above the pipe
and heatsink assembly.
2. Fit the grooved edge to the
heatsink.
3. Carefully push down the fan until
it snugly fits the heatsink, then
connect the fan cables.
• Plug the optional fan cables to the CHA_FAN and/or PWR_FAN connector
on the motherboard.
• Make sure the optional fan is installed correctly to prevent damage to the
fan and motherboard components.
4. The above photo shows the fans
installed on the motherboard.
Do not tilt the fan.
Do not install the fan with its rear
side facing you.